Dissipative quantum–oscillator with two competing heat baths

We study the dissipative dynamics of a harmonic oscillator which couples linearly through its position and its momentum to two independent heat baths at the same temperature. We argue that this model describes a large spin in a ferromagnet. We find that some effects of the two heat baths partially cancel each other. This leads to unexpected features such as underdamped oscillations in the strong coupling regime. Such a partial frustration of dissipation can be ascribed to the canonically conjugate character of position and momentum. We compare this model to the scenario where a single heat bath couples linearly to both the position and the momentum of the central oscillator. In that case no surprising behavior occurs for strong coupling. The dynamical evolution of the quantum purity for a single and a double wave packet is also investigated. PACS numbers: 03.65.Yz, 05.40.-a † Institut für theoretische Physik, Philosophenweg 19 Universität Heidelberg, Germany ‡ Departamento de F́ısica de Materiales , Universidad Complutense de Madrid, E-28040 Madrid, Spain E-mail: [email protected],[email protected] Submitted to: New J. Phys. Dissipative quantum–oscillator with two competing heat baths 2